Semiconductor devices such as microcomputers, memories, gate arrays, among others, rely on power to operate. One or more power supplies are used to provide power to the semiconductor device. When power is initially provided to a semiconductor device, for example, at power up or system reset, a supply voltage provided by the power supply ramps up from a zero voltage to a nominal supply voltage. Operation of the circuits of the semiconductor device should be suppressed until the power provided by the power supply is sufficient for the circuits to operate correctly. Operation of circuits prior to when sufficient power is provided may result in the circuits failing to operate correctly.
Voltage detections circuits may be included in a semiconductor device to determine when the supply voltage reaches a minimum voltage assumed to be sufficient for the circuits to operate correctly. However, relying simply on the voltage of the supply voltage to determine sufficiency of power may nonetheless not be an adequate measure.